1. Field of the Invention
The present invention relates generally to the monitoring and control of metering systems. More particularly, the present invention relates to an intelligent electronic device configured to generate a serial message using a DNP protocol and to transmit this message via an Ethernet medium.
2. Discussion of the Related Prior Art
The metering architecture that exists in the power utility field today is geared toward providing enough information to accurately monitor and control a variety of metering devices installed at numerous substations. To achieve these objectives, it is essential that communication between a central utility station and substations be time-and cost-efficient, quick updating, as well as reliable.
Historically, meters measuring electrical energy have used measurement devices, which mechanically monitor the subscriber's usage and display a reading of the usage at the meter itself. Consequently, the reading of these meters has required that human meter readers physically go to the site of the meter and manually document the readings. Clearly, this approach relies very heavily on human intervention and, thus, is very costly, time-consuming, and prone to human error. As the number of meters in a typical utility's service region has increased, in some cases into the millions, human meter reading has become prohibitive in terms of time and money.
Over time, these conventional meters were made using microprocessor technologies, which enabled them to be read using a serial protocol and interface. This enabled the meters to be used in series to obtain readings back at a remote terminal unit (RTU) for remote SCADA (Supervisory Control and Data Acquisition) interrogation. For example, FIG. 1 is a schematic view of a conventional system for monitoring and controlling a plurality of substations. That is, referring to FIG. 1, meters 1, 2, and 3 can communicate serially through each other. However, in order for a SCADA master 5 to receive information from meter 3, the information must be passed from meter 3 to meter 2, from meter 2 to meter 1, from meter 1 to an RTU 4, and from the RTU 4 to the SCADA master 5.
Realization of such communication may be accomplished by a standard open protocol known as DNP 3.0. This protocol is configured to provide the power utility with a serial language to speak to the substations and to allow the utility to use outage detection software, generically labeled in the industry as SCADA. In other words, communication between each of the meters and, for example, a central station is realized through a respective serial port and is thus limited to a respective pair coupled to one another via a dedicated channel.
Originally the SCADA systems have been provided with generally UNIX-based software operative to establish communication only between RTUs, which originally were embedded devices operative to bring in analog inputs and provide digital outputs. Accordingly, all analog telemetry was brought to the RTU and then converted to a digital signal subsequently formatted and transferred to the SCADA master. With the advent of digital communication technology, a variety of intelligent electronic devices (IED) including, but not limited to, metering, protective relays, apparatus equipment, and controllers, have become operative to communicate a digital serial protocol though a plurality of dedicated channels.
One disadvantage of this approach may have been that when a number of meters transmit meter data nearly simultaneously, the inherent latency on the area network including a plurality of dedicated serial channel or dedicated cables results in packet collisions, lost data, garbled data, and general degradation of integrity across the system. To compensate for the collisions and interference between data packages destined for the central computer, due to the latency inherent in this system, various management schemes have been employed to ensure reliable delivery of the meter data. However, while this approach may be suitable for small systems, it does not serve the needs of a utility monitoring thousands or even millions of meters.
Therefore, a need exists to provide a system whereby a utility company can reliably and rapidly read on the order of innumerous meters in the absence of any significant human intervention. Further, a need exists to provide a system configured with multiple IED devices that are capable of communicating via Ethernet TCP/IP by using the DNP 3.0 protocol through an open socket within the Ethernet TCP/IP medium.